A stent is generally a longitudinal tubular device formed of biocompatible material, which is useful to open and support various lumens in the body. Stents are used in various bodily passageways, such as in the coronary or peripheral vasculature, esophagus, trachea, bronchi, colon, biliary tract, urinary tract, prostate, brain, as well as in a variety of other applications in the body. These devices are implanted within the passage to open and/or reinforce collapsing or partially occluded sections. While stents and other intraluminary prosthesis are foreign objects to the human body, they are designed to remain within a body passageway for prolonged periods or even indefinitely.
Stents generally include a flexible configuration. This configuration allows the stent to be inserted through curved vessels or lumens (natural or artificial) and curved instruments, such as an endoscope. Such stents are generally delivered using a flexible elongate catheter. The catheters are designed to resist kinking and may be developed with various levels of stiffness. The stents are designed and configured to radially compress for intraluminary catheter implantation. Once properly positioned adjacent the damaged vessel or lumen, the stent is radially expanded so as to support and reinforce the vessel or lumen. Radial expansion of the stent may be accomplished by inflation of a balloon or other expanding means attached to the catheter or the stent may be of the self-expanding variety which will radially expand once deployed.
Tubular shaped structures, which have been used as intraluminary vascular stents, have included helically wound coils which may have undulations or zigzags therein, slotted stents, ring stents, braided stents and open mesh wire/filament stents, to name a few. Additionally, super-elastic and shape memory materials using plastic and/or metals have also been used to form stents.
Diagnosis and treatment in patients of biliary strictures caused by malignant or benign biliary disease is treatable. A patient with biliary disease typically suffers from an obstruction in the pancreaticobiliary ductal system. Numerous diseases can cause the inability of bile flow, however, the presence of gallstones and/or strictures appear the most prevalent reason. For benign strictures, stenting is one possible solution. In particular, tubular stents are used in bile, pancreatic and hepatic ducts where a solid stent is needed and where in-growth can occur due to proliferating oncologous cells.
Solid stents are often mounted on a balloon catheter and delivered non-invasively, such as through an endoscope, and deployed by expanding the stent to a larger diameter. For example, U.S. Pat. No. 5,191,883 to Lennox et al. and U.S. Pat. No. 6,830,559 to Schock describe balloon catheter delivery systems. Alternatively, the stent is slipped off a catheter with no expansion. For example, see U.S. Pat. No. 5,334,185 to Giesy et al. These stents are typically designed to withstand drastic deformations as it is conveyed through the twists and turns of the tortuous anatomy of a patient's gastrointestinal system.
One drawback, however, is that as the delivery system is tracked through the endoscope, the stent may slide out of its intended position. In particular, a stent may slide proximally and may no longer be disposed between radiopaque markers on and/or the electrodes used to expand the balloon located on the delivery system. Thus, once out of position, the physician may find it difficult to accurately position the stent. Also, the stent may be difficult to properly expand if improperly positioned on the balloon.
Additionally, even when the stent remains properly positioned on the delivery system, removal of the balloon after delivery can sometimes be problematic. After the stent has been fully expanded, the balloon is generally deflated before being removed. While or after being deflated, however, the balloon may get stuck to the stent. Sticking can occur due to anatomical curvatures in the delivery location which pinch or trap the balloon, stent to balloon material tackiness, a balloon wing fold getting hung-up and/or other reasons. During removal, if the balloon is stuck to the stent it can slightly pull the stent out of place or even completely out of position.
Therefore, there is a need for improved delivery systems for stents deployed using an expansion member, such as a balloon catheter. Such a system preferably overcomes the shortcomings set forth above while being relatively easily manufactured and used.